Laser photolysis studies on CuI complexes of thia-calix[3]pyridine. Phosphorescence from the intramolecular charge-transfer excited state

Synthesis, Structure, and Characterization of Thiacalix[4]-2,8-thianthrene

Sulfur-containing macrocycles have attracted substantial interest because they exhibit unique characteristics due to their polygonal ring-shaped skeleton. In this study, a thianthrene-based cyclic tetramer with the sulfur linker, thiacalix[4]-2,8-thianthrene (TC[4]TT), was successfully prepared from a cyclo-p-phenylenesulfide derivative using acid-induced intramolecular condensation. Single crystal X-ray diffraction revealed that TC[4]TT adopts an alternative octagonal form recessed to the inner side. Its internal cavity included small solvents, such as chloroform and carbon disulfide. Due to its polygonal geometry, TC[4]TT laminated in a honeycomb-like pattern with a porous channel. Furthermore, TC[4]TT showed fluorescence and phosphorescence emission in a CH₂Cl₂ solution at ambient and liquid nitrogen temperatures. Both emission bands were slightly redshifted compared with those of the reference compounds (di(thanthren-2-yl)sulfane (TT₂S) and thianthrene (TT)). This work describes a sulfur-containing thiacalixheterocycle-based macrocyclic system with intriguing supramolecular chemistry based on molecular tiling and photophysical properties in solution.

Spectral and thermodynamic properties for the exciplexes of N-alkyl carbazoles with dicyanobenzenes in THF

The exciplex emission spectra of N-ethylcarbazole with 1,2-dicyanobenzene (NEC/1,2-DCB), N-methylcarbazole with 1,2-dicyanobenzene (NMC/1,2-DCB), 1,3-dicyanobenzene (NMC/1,3-DCB), and 1,4-dicyanobenzene (NMC/1,4-DCB) are studied in tetrahydrofuran (THF) for the temperature range starting from 253 K to 334 K. Thermochromic shifts along with the spectral properties including change in peak intensities and the ratio of exciplex peak intensity to fluorophore peak intensity are studied. Effect of temperature on the energy of zero-zero transitions hνo('), Huang-Rhys factor (S), Gauss broadening of vibronic level (σ) and the dominant high-frequency vibration (hνν) are also part of investigation. Enthalpy of exciplex formation (ΔH(EX)(∗)) calculated by the model proposed by A. Weller and the Gibb's energy of electron transfer (ΔG(et)(∗)) for all exciplex systems are also discussed in the present paper. All the exciplexes under study were observed to be dipolar in nature. The exciplex of the N-methylcarbazole/1,4-dicyanobenzene was found to be the most stable and the N-methylcarbazole/1,3-dicyanobenzene was the weakest exciplex system.

Selective oxygenation of amphiphilic thiacalix[3]pyridine Rh(i) diene complexes in both water and organic solvents

Thiacalix[3]pyridine (Py3S3) reacted with [Rh(diene)(mu-Cl)]2(diene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene (nbd)) to give amphiphilic trigonal bipyramidal complexes, [Rh(Py3S3)(diene)]Cl. Sulfur bridges of the Py3S3 ligand in these complexes were selectively oxygenated by m-chloroperoxybenzoic acid in dichloromethane to give sulfinylcalix[3]pyridine complexes, [Rh(Py3(SO)3)(diene)]+, in which all three oxygen atoms of the SO groups occupy the equatorial positions. Structures of the complexes were analysed by X-ray crystallography and the oxidation reaction was investigated using 1H NMR spectroscopy and electrospray ionisation mass spectrometry showing that the oxygenation of the sulfur atoms in the ligand proceeded stepwise and further oxygenation of the SO moiety occurred only for the nbd complex having the smaller diene ligand resulting in [Rh(Py3(SO)2(SO2))(nbd)]+. On the other hand, the oxidation of [Rh(Py3S3)(cod)]+ by H2O2 in water did not result in oxygenation of the sulfur bridges but the cod ligand is hydroxygenated to give 1,4,5,6-eta4-2-hydroxycycloocta-4-ene-1,6-di-yl.